Fluid pressure brake



April 26, 1938. J cANETTA 2,115,515

FLUID PRESSURE BRAKE Filed June 30, 1936 2 Sheets-Sheet l INVENTOR \JOHN OAN ET TA April 26, 1938. .1. CANETTA 2,115,515.

7 FLUID PRESSURE BRAKE Filed June 50, 1936 2 Sheets-Sheet 2 Q4 Q6 I00 7INVENTOR d OH N CAN ETTA BY%W ATTORNEY Patented Apr. 26, 1938 UNITEDSTATES PATENT OFFlCE FLUID PRESSURE BRAKE Application June 30, 1936,Serial No. 88,130

27 Claims.

This invention relates to a fluid pressure brake and more particularlyto an improvement in the brake controlling valve device shown in thecopending application Serial No. 67,274, of Ellery R.

5 Fitch, filed March 5, 1936.

The brake controlling valve device shown in the above identifiedapplication has a movable abutment subject to the opposing pressures ofthe fluid in the brake pipe and of the fluid in a pressure chamber forcontrolling emergency applications of the brakes and for controlling apassage through which fluid under pressure may be supplied from thebrake cylinder to the brake pipe. This valve device has, in addition, apassage controlled by the movable abutment and through which fluid underpressure may flow from the pressure chamber to the brake pipe at a ratewhich will permit the pressure of the fluid in the pressure chamber toreduce substantially as rapidly as the pressure of the fluid in thebrake pipe is reduced on a reduction in brake pipe pressure at a servicerate to thereby prevent the development of suflicient difierentialbetween the pressures in the pressure chamber and in the brake pipe tocause the movable abutment to be moved to a position in which theemergency valve device is operative to effect the venting of fluid underpressure from the brake pipe and thereby cause an emergency applicationof the brakes.

This passage, however, is of insuflicient flow capacity to permit fluidunder pressure to flow from the pressure chamber to the brake piperapidly enough to permit the pressure of the fluid in the pressurechamber to reduce as rapidly as the pressure of the fluid in the brakepipe is reduced when the brake pipe pressure is reduced at an emergencyrate. As a result, a differential in the pressures in the pressurechamber and in the brake pipe will be developed, and the movableabutment will move to emergency application position and by thismovement it will cut oil communication between the pressure chamber andthe brake pipe.

Upon a subsequent increase in the pressure of the fluid in the brakepipe to eiTect the release of the brakes, the abutment is moved from theapplication position to the release position and on this movement of theabutment, the passage between the brake pipe and pressure chamber isopened so as to permit fluid under pressure to flow to the pressurechamber to restore the pressure of the fluid in the pressure chamber.

There is a possibility, if the rate of increase in the pressure of thefluid in the brake pipe after an application is relatively slow,'thatthe movable abutment will not move far enough from the applicationposition towards the release position to completely open the passagebetween the brake pipe and the pressure chamber, but will only move farenough to partially open this passage, which, however, will permit.fluid under pressure to flow from the brake pipe to the pressure chamberrapidly enough to increase the pressure of the fluid in the pressurechamber as rapidly as the pressure of the fluid in the brake pipe isincreased. 10 As a result, there may not be a sufficient differentialdeveloped between the pressure of the fluid in the brake pipe and in thepressure chamber to cause further movement of the abutment towards therelease position, and the abutment 15 may remain in'a position in whichit only partially opens the communication between the brake pipe and thepressure chamber.

If this condition occurs, then on a subsequent reduction in the pressureof the fluid in the brake 20 pipe at a service rate to effect a serviceapplication of the brakes, fluid under pressure will be unable to flowfrom the pressure chamber to the brake pipe rapidly enough, because thepassage between the pressure chamber and the brake 25 pipe islonlypartially opened, to permit the pressure of the fluid in the pressurechamber to re-v duce as rapidly as the pressure of the fluid in thebrake pipe is reduced.

As a result upon a reduction in brake pipe pres- 30 sure at a servicerate there will be a constantly increasing difference between thepressure of the fluid in the brake pipe and the pressure of the fluid inthe pressure chamber and a suflicient differential may be provided inthe brake pipe 35 and the pressure chamber and the higher pressure inthe pressure chamber will cause the abutment to move to its applicationposition and thereby produce an undesired emergency application of thebrakes. 40

It is an object of this invention to provide a brake controlling valvedevice operative to efiect an emergency application 01": the brakes andhaving a movable abutment subject to the opposing pressures of the fluidin the brake pipe and of the 45 fluid in a pressure chamber, theabutment controlling a communication through which fluid under pressuremay flow between the brake pipe and the pressure chamber, means beingprovided to insure that after an emergency application of 50 the brakes,the abutment will move the entire distance from the application positionto the release position.

A further object of the invention is to provide a brake controllingvalve device of the type re- 55 ferred to and having means responsive tothe pressure of the fluid supplied from the brake pipe to the passageleading from the brake pipe to the pressure chamber for controlling theflow of fluid through this passage, said means being adapted to preventthe flow of fluid to the pressure chamber through this passage until thebrake pipe pressure has been increased to a predetermined value which ishigh enough to insure that the movable abutment will move all of thedistance from the application position to the release position.

A further object of the invention is to provide an emergency valvedevice having a movable abutment subject to the opposing pressures ofthe fluid in the brake pipe and of the fluid in a pressure chamber andcontrolling a passage through which fluid under pressure may flowbetween the brake pipe and the pressure chamber and having an abutmentsubject to the pressure of the fluid supplied from the brake pipe tothis passage for controlling communication through this passage togetherwith valve means operated by this abutment for venting fluid from thepressure chamber.

Another object of the invention is to provide an emergency valve devicehaving a movable abutment subject to the opposing pressures of the fluidin the brake pipe and of the fluid in a pressure chamber and controllinga passage through which fluid may flow from the brake cylinder to thebrake pipe and also controlling a passage through which fluid may flowbetween the brake pipe and the pressure chamber, and having an abutmentsubject to the pressure of the fluid supplied from the brake pipe to thelast named passage for controlling communication therethrough, togetherwith valve means operated by said abutment and controlling the passagethrough which fluid is supplied from the brake cylinder to the brakepipe,

A further object of the invention is to provide an improved brakecontrolling valve device.

Other objects of the invention and features of novelty will be apparentfrom the following description taken in connection with the accompanyingdrawings, in which Fig. 1 is a fragmentary view of a brake equipmentemploying a brake controlling valve device embodying this invention, and

Fig. 2 is a fragmentary view of a brake equipment employing another formof brake controlling valve device embodying this invention.

Referring to the drawings the brake equipment illustrated in Fig. 1thereof comprises a brake pipe I, a brake cylinder 2, an emergencyreservoir 4, and a brake controlling valve device indicated generally bythe reference numeral 5.

The brake controlling valve device 5' comprises a pipe bracket section 1having a mounting face thereon against which is secured the emergencyvalve portion 8 provided by this invention, while the pipe bracketsection has another mounting face formed thereon, (not shown), againstwhich is secured the service portion, (not shown), of the brakecontrolling valve device.

The emergency portion of the brake controlling valve device provided bythis invention is an improvement on the corresponding section of thebrake controlling valve device shown and claimed in U. S. Patent No.2,301,213, to Clyde C. Farmer, and only such portions of theconstruction and operation of the valve device are illustrated anddescribed in this application as are essential to the understanding ofthis improvement.

The emergency valve portion 8 comprises a body having a bore therein inwhich is mounted a movable abutment in the form of a piston I0 having atone side thereof a chamber l2, which is connected by way of a passage [3in the pipe bracket section 1 with a branch pipe l4 which communicateswith the brake pipe I.

The piston ID has at the other side thereof a valve chamber IS in whichis mounted a main slide valve 18 and an auxiliary slide valve 20 whichare operated by the piston I0 through a stem 22 formed integral with thepiston. The valve chamber [6 is connected by Way of a passage l5 with apressure chamber l1 formed in the pipe bracket section 1.

The stem 22 has a bore in the end thereof in which is mounted a plunger24 which is yieldingly pressed against the end of the main slide valvel8 by means of a spring 26.

The end of the valve chamber [6 is closed by means of a cover 28 andthis cover has a bore therein, in which is mounted a plunger 30 which isadapted to be engaged by a shoulder 32 on the piston stem 22, and by aprojection 34 on the end of the main slide valve l8. The plunger 30 isyieldingly urged to the right, as viewed in the drawings, by means of acoil spring 36 while movement of the plunger in this direction islimited by engagement of the plunger 30 with the body of the emergencyportion.

The main slide valve 18 is held in engagement with its seat by means ofa strut 38 which engages one face of a diaphragm 40. The other face ofthe diaphragm 40 is subject to the pressure of the fluid in a chamber 42which is constantly connected by way of a passage and pipe 44 with theemergency reservoir 4. The diaphragm 40 is also subject to the pressureof a spring 46 which is mounted in the chamber 42.

The body of the emergency portion 8 has formed therein a chamber 48 inwhich is mounted a spill-over check valve 50 which is yieldingly urgedby means of a spring 52 into engagement with a seat rib 54.

The chamber 48 is constantly connected with I the passage 44 and therebywith the emergency reservoir 4, while the chamber within the seat rib 54has positioned therein a ball check valve 55 which is adapted to engagea seat formed on the body surrounding a passage 58 which communicateswith the valve chamber it.

The body of the emergency portion 8 also has formed therein a chamber 65which is constantly connected by way of a passage 52 with the passage |3in the pipe bracket section l and thereby through the branch pipe [4 tothe brake pipe 1. An accelerated release check valve 54 is mounted inthe chamber and is yieldingly urged by means of a spring 66 intoengagement with a seat rib 68, while a ball check valve TB is mounted inthe chamber within the seat rib 68 and is adapted to engage a seatformed on the body surrounding a passage 12 which communicates with aport in the seat of the main slide valve IS.

The body of the emergency portion 8 also has a bore therein in which ismounted a vent valve piston 16 having at one side thereof a chamber 18which is constantly connected by way of a passage 80 with a port in theseat of the main slide valve I8.

The chamber on the other face of the piston 16 is open to the atmosphereby way of a passage 82, while the body has a groove 84 cut therein,which, in one position of the piston 16, extends around the piston so asto permit communication between the chamber 18 and the chamber on theopposite face of the piston I6.

The piston 16 has a passage 86 extending therethrough so as to permitfluid to flow from the chamber I8 to the chamber on the opposite face ofthe piston and thence to the atmosphere by way of the passage 82. Thepassage 86 has a choke 88 interposed therein to restrict the rate offlow of fluid from the chamber I8.

The body of the emergency valve portion has secured in a groove thereinadjacent the vent valve piston a sealing gasket 99 having formed thereonan annular seat rib 92 which is adapted to be engaged by a face of thepiston 16 to cut off communication from the chamber 18 around theperiphery of the piston I6.

The piston 16 has formed integral therewith a stem 94 which has securedthereon a ventvalve 99, which is mounted in a chamber 91 formed in thebody of the emergency portion 8, and which is adapted to engage a seatrib 98 formed on the body of the emergency portion 8. The chamber 91 inwhich the valve 96 is mounted is connected by way of a passage 99 withthe passage. 62 and thereby with the passage I3 in the pipe bracketsection I to which is connected the branch pipe I 4 leading to the brakepipe I, while the valve 96 is yieldingly urged by means of the springI99 into engagement with the seat rib 98. I i

The emergency portion shown in this application incorporates means tocontrol the supply of fluid under pressure from. the brakepipe to thevalve chamber I6 and the pressure chamber I1 and to also control therelease of fluid under pressure from the valve chamber I6 and thepressure chamber N. This means comprises a valve device indicatedgenerally by the reference numeral I92.

The valve device I92 forms no part of this invention, but is theinvention of H. R. Feuhrer, and is shown and claimed in his applicationSerial No. 88,075, filed June 30, 1936.

The valve device I92 comprises a valve I 94 which is mounted in achamber I96 which is com stantly connected by way of a passage I98 withthe valve chamber I6 and the pressure chamber I I. The valve I94 isyieldingly held away from the seat rib II 9 surrounding a chamber II2 bymeans of a spring I I4.

The valve I94 is adapted to be moved to the seated position by means ofa diaphragm II6 which is subject on one side to the pressure of thefluid in the chamber I96 and on. the other side to the pressure of thefluid in a chamber I I8. The diaphragm H6 is engaged on one face by thehead of a plunger I29 having a bore therein in which is mounted a springseat I22 carrying a stem I24 which engages the valve I94. The

spring seat I22 is engaged by a spring I26, while movement of the springseat I22 by the spring I26 is limited by engagement of the spring seatwith a shoulder I28 on the plunger I29. The spring I26 is proportionedso as to be able to transmit substantially greater force to the valveI94 than is exerted by the spring II4 so that the valve I94 may be movedby the spring I26 against the spring I I4 to the seated position. Thespring I26 provides a yielding force transmitting means, whereby thevalve I94 is held seated with a substantially constant pressureregardless of the extent of movement of the diaphragm I I6.

The body of the emergency valve portion 8 has projections I29 formedthereon and extending into the chamber H8 and adapted to be engaged by aface of the diaphragm II6 to limit movement of the diaphragm in onedirection, while the head of the plunger I29 is adapted to engageshoulders I 39' on the body of the valve portion to limit movement ofthe plunger I29 and the diaphragm H6 in the other direction.

The emergency portion provided by this invention has valve meansindicated generally by the reference numeral I32 for controlling thesupply of fluid under pressure from the brake pipe to the valve chamberI6 and the pressure chamber I1. As shown in the drawings, the valvemeans I32 comprises a diaphragm I34 which is urged into engagement witha seat rib I36 by means of a spring I38 mounted in a chamber I49 whichis constantly connected with the atmosphere by way of a passage I42, aspring seat I39 being interposed between the spring I38 and thediaphragm I34.

The chamber I44 within the seat rib I36 is constantly connected by wayof a. passage I46 with the chamber H8 at the face of the diaphragm I I6, and is connected by way of a passage I48 with a port in the bore inthe body of the valve portion in which the piston I9 is mounted. Thepassage I48 has a choke I59 interposed therein.

The chamber I52 outwardly of the seat rib I36 is connected by way of apassage I54 with the chamber I I2, while a passage I56, having a chokeI58 interposed therein, communicates with the passage I54 andwith thepassage I98 leading to the valve chamber I6 and the pressure chamber I1.The choke I58 is of substantially smaller flow capacity than the chokeI59.

The emergency valve portion shown in Fig. 1 of the drawings is shown inthe normal release position, which is the position which it assumes whenthe brake equipment is fully charged. When the brake equipment is atatmospheric pressure the diaphragm I 34 is held in engagement with theseat rib I36 by the spring I38, while the other parts of the emergencyvalve portion may be in the position in which they are shown in thedrawings.

In initially charging the equipment fluid under pressure is supplied tothe brake pipe I and it flows therefrom through the branch pipe I4 tothe passage I3 and to the chamber I2 on the face of the piston I9.

Fluid under pressure supplied to the passage I3 also flows to theservice portion- (not shown) of the brake controlling valve device 5,and causes the piston of this portion to move to the release position inwhich the brake cylinder 2 is connected to the atmosphere, and in whicha communication is opened through which fluid under pressure may flowfrom the passage I3 to the auxiliary reservoir (not shown) and to theemergency reservoir 4 to charge these reservoirs with fluid underpressure.

Fluid under pressure supplied by the service portion of the brakecontrolling valve device to the emergency reservoir 4 flows by way ofthe passage 44 to the chamber 42 on the face of the diaphragm 49 andincreases the force exerted through the stem 38 to maintain the mainslide valve I8 in engagement with its seat.

Fluid under pressure supplied to the passage 44 also flows to thechamber 48, but, as the check valve 59 is maintained in the seatedposition by the spring 52, fluid under pressure cannot flow from thechamber 48 to the valve chamber I6.

Fluid under pressure supplied from the brake pipe I to the passage I3flows therethrough to the chamber I2 on the face of the piston I9 of theemergency valve portion 8, and on an increase in the pressure of thefluid in this chamber the piston ID will be moved to the left, as viewedin Fig. 1 of the drawings, to the normal release position, if it is notalready in that position, which is the position in which it is shown inthis figure of the drawings. On movement of the piston I0 to the normalrelease position, communication is opened between the chamber I2 and thepassage I48 through the choke I50 and fluid under pressure will flow tothe chamber I44 on the face of the diaphragm I34, which at this time isheld in engagement with the seat rib I36 by the spring I38. The springI38 is of such value, and the chamber I44 within the seat rib I36 is ofsuch area, that the diaphragm I34 is held in engagement with the seatrib I36 until the pressure of the fluid in the chamber I44 within theseat rib I36 has increased to a predetermined value.

On an increase in the pressure of the fluid in the chamber M4 fluidunder pressure flows therefrom by way of the passage I46 to the chamberI I8 on the face of the diaphragm I I6.

On a predetermined increase in the pressure of the fluid in the chamberN8 the diaphragm H6 is moved upwardly, as viewed in the drawings,thereby moving the plunger I26 upwardly, and this movement of theplunger S20 is transmitted through the spring I26 to the, Spring seatI22 to press the stem I24 against. the valve I04 and move this valveagainst the spring II4 into engagement with the seat rib IIll. Onmovement of the valve I64 to the seated position, and on furthermovement of the plunger I20, the spring I26 is compressed and theplunger I20 is moved relative to the spring seat I22. The plunger 523may continue to move in this direction until the head of the plunger I26engages the shoulders I3Il on the body of the emergency valve portion 8.

The increase in the pressure of the fluid in the chamber I44 will beaccompanied by a similar increase in the pressure of fluid in thechamber I2 on the face of the piston I6 and the fluid under pressure inthis chamber exerts a force on the piston I6 tending to move it to theleft, as viewed in Fig. l of the drawings, to the normal releaseposition.

The spring i313 and the other portions of the valve means I32 areproportioned so as to maintain the diaphragm I34 in engagement with theseat rib I36, and thereby prevent the flow of fluid under pressure fromthe brake pipe to the valve chamber I6 and the pressure chamber I'I,until the pressure of the fluid in the chamber I2 on the face of thepiston IE] has increased to a value such that the force exerted on thepiston II! will cause full movement of the piston I6 to fully open theport through which the passage I46 communicates with the chamber I2.

Movement of the piston Ill farther to the left, as viewed in thedrawings, from the normal release position to the inner release positionis resisted by the spring 36 acting through the plunger 36 which isengaged by the shoulder 32 on the piston stem 22 and by the projection34 on the main slide valve I8. The various parts of the valve portionprovided by this invention are arranged, however, so that the spring 36and the plunger 39 are not effective to oppose movement of the pistonII] in this direction until the piston III has moved to a position tocompletely open the port through which the passage I43 communicates withthe chamber I2 on the face of the piston I0.

When the pressure of the fluid in the chamber I44 on the face of thediaphragm I34 has increased to a predetermined relatively high value theforce exerted by the fluid under pressure in the chamber I44 on thediaphragm I34 is sufficient to overcome the opposing force of the springI38, and the diaphragm I34 will be moved away from the seat rib I36 soas to permit fluid under pressure toflow from the chamber I44 past theseat rib I36 to the chamber I52 outwardly of the seat rib I36.

When the diaphragm I34 is moved away from the seat rib I36 and fluidunder pressure is supplied to the chamber I52 outwardly of the seat ribI36 the entire area of the face of the diaphragm I34 is subjectto thepressure of the fluid in the chambers I44 and I52, and the force exertedby this fluid under pressure on the diaphragm I34 will be substantiallygreater than that exerted by the fluid under pressure in chamber I44within the seat rib I36. As soon as the diaphragm I34 is moved away fromthe seat rib I36, therefore, there is a substantial increase in theforce exerted by the fluid under pressure on this diaphragm, and thediaphragm is thereafter moved very quickly against the spring I38 untilthe spring seat I39 engages a portion of the body of the emergency valve8 to prevent further movement of the diaphragm I34 against the springI38.

On the supply of fluid under pressure to the chamber I52 outwardly ofthe seat rib I36, fluid under pressure flows therefrom by way of thepassagel54 to the chamber M2 on the spring side'of the valve I04.However, at this time the valve I64 is held in the seated position bythe diaphragm II6 acting through the plunger I20 and fluid underpressure cannot flow from the chamber II2 past the seat rib III! to thechamber I06.

Fluid under pressure supplied to the passage I54 flows therefrom to thepassage I56 and through the choke I58 to the passage I68 through whichit flows to the chamber I06 on the face of the diaphragm H6, and to thevalve chamber I6 and by way of the passage I5 to the pressure chamber I!to increase the pressure of the fluid in these chambers.

The choke I58 is proportioned so as to restrict the rate of flow offluid from the chamber I2 to the valve chamber I6 and the pressure chamber IT to a very slow rate so that there will be a slow increase in thepressure of the fluid in these chambers. As a result, the pressure ofthe fluid in the chamber I2 on the face of the piston ID will increasemore rapidly than the pressure of the fluid in the chamber I6 on theopposite side of the piston I6 so that there will be a constantlyincreasing difference between the pressures in the chambers I2 and I6 onthe opposite sides of the piston I6. There will, therefore, be aconstantly increasing force exerted on the piston I0 and tending to moveit to the left, as viewed in the drawings, against the opposing force ofthe spring 36, and the piston ill will be moved in this directionagainst the spring 36 to the inner release position.

After a time interval the pressure of the fluid in the valve chamber I6and in the pressure chamber I! will have increased by the flow of fluidthereto through the choke I58 to a value such that the force exerted bythe fluid under pressure in the valve chamber I6, together with theforce exerted by the spring 36 acting through the plunger 30, will beable to overcome the opposing force exerted on the piston I by the fluidunder pressure in the chamber I 2.

When the pressure of the fluid in the chamber I6 has increased to thisvalue the piston I0 will be moved to the right, as viewed in thedrawings, from the inner release position to the normal release positionby the fluid under pressure in the chamber I6, and by the spring 36acting through the plunger 30. When the piston I has been moved to thenormal release position the plunger 30 engages a portion of the body ofthe emergency valve portion 8 so that the spring 36 is no longereffective to assist movement of the piston I0, and further movement ofthe piston I0 by the fluid under pressure in the valve chamber IE willbe opposed by the higher pressure in the chamber I2. The plunger 30engages the projection 34 on the main slide valve I8 and on thismovement of the plunger 30 by the spring 36 the main slide valve I8 ismoved on its seat.

The plunger 30 engages a portion of the body of the emergency portion 8so as to prevent further movement of the piston I0 by the spring 36before the piston I0 has been moved to a position to restrictcommunication through the port through which the passage I48communicates with the chamber I2 on the face of the piston I0. Thepiston I0, therefore, will be maintained in a position to permitunrestricted communication through the port leading from the chamber I2to the passage I48.

After the piston I0 has been moved from the inner release position tothe normal release position, which is the position in which it is shownin the drawings, fluid under pressure continues to flow from the chamberI2 on the face of the piston I0 through the choke I50 to the passage M8leading to the chamber I44, thence past the seat rib I36 to the chamberI52 outwardly of the seat rib I36, and therefrom by way of the passageI54 to the passage I56 and through the choke I58 to the passage I08leading to the valve chamber I6 and the pressure chamber I1 and to thechamber I6 and increases the pressure of the fluid in these chambersuntil the pressures therein have substantially equalized with thepressure of the fluid in the chamber I2.

If the pressure of the fluid in the valve chamber I6 increases morerapidly than the pressure of the fluid in the emergency reservoir 4,fluid under pressure will flow from the valve chamber I6 through thepassage 58 and past the ball check valve 56 to the chamber within theseat rib 54 and it will move the spill-over check valve 50 away from theseat rib 54 against the spring 52 and the pressure of the fluid in thechamber 46 so as to permit fluid under pressure to flow to the chamber48. Fluid under pressure supplied to the chamber 48 flows therefrom byway of the passage and pipe 44 to the emergency reservoir 4.

When the pressure of the fluid in the valve chamber 86 has reducedsubstantially to the pressure of the fluid in the emergency reservoir 4the spill-over check valve 50 is moved to the seated position by thespring 52 tocutoff the flow of fluid from the valve chamber I6 to theemergency reservoir and to prevent back flow of fluid from the emergencyreservoir 4 .to the valve chamber I6.

On an increase in the pressure of the fluid in the chamberv I06 on theface of the diaphragm H6, there is an increase in the force exerted bythe fluid in this chamber on the diaphragm H6 and opposing the forceexerted by the fluid under pressure in the chamber H8 on the oppositeface of the diaphragm I I6. When the pressure of the fluid in thechamber I06 has increased approximately to the pressure of the fluid inthe chamber H8 on the opposite face of the diaphragm H6, which issubstantially at the same pressure as the fluid in the chamber I2 on theface of the piston I0, the force exerted by the fluid under pressure inthe chamber I06, supplemented by the force exerted by the spring I26acting through the plunger I20, will be sufficient to overcome theopposing force of'the fluid under pressure in the chamber I I8 and thediaphragm I I6 will be moved downwardly, as viewed in Fig. 1 of thedrawings, thereby permitting the spring I26 to expand.

The spring I26 will expand until the spring seat I22 engages theshoulder I28 on the plunger I20, and it will thereafter be Ineffectiveto exert force on the diaphragm H6 and tending to move the diaphragmagainst the opposing force of the fluid under pressure in the chamberH8.

However, the spring H4 is now effective to assist movement of thediaphragm H6 against the opposing force of the fluid under pressure inthe chamber H8, but the spring H4 is substantially weaker than thespring I26 and exerts substantially less force than the spring I 26exerted.

On a slight further increase in the pressure of the fluid in the chamberI06, which is at substantially the same pressure as the fluid in thechambers I6 and H, the force exerted by the fluid under pressure in thechamber I66 supplemented by the force exerted by the spring I I4 actingthrough the valve I04 and the spring E26 will be suflicient to move thediaphragm H6 against the opposing force of the fluid under pressure inthe chamber H8, and the diaphragm H6 will thereupon be moved downwardlyinto engagement with the projections I29.

On this movement of the diaphragm II 6 the stem I24 of the spring seatI22 is moved downwardly, thereby permitting the spring H4 to move thevalve I04 away from the seat rib I l0 and permit fluid under pressuresupplied by the valve means I32 to the passage I54 and there from to thechamber H2 within the seat rib H0 to flow past the seat rib H0 to thechamber I06 and thence by way of the passage I06 to the chambers I6 andI1.

When the valve I4 is moved away from the seat rib H0 fluid underpressure may flow at a rapid rate from the chamber H2 to the chamber I66and thence by way of the passage I 66 to the chambers I6 and H, with theresult that the pressure of the fluid in the chambers I6 and I! willquickly equalize with the pressure of the fluid in the chamber I2 on theface of the piston I0.

Upon a subsequent reduction in the pressure of the fluid in the brakepipe I at a service rate to effect a service application of the brakes,the service portion (not shown) of the brake controlling valve deviceoperates as described in detail in the above identified patent to closethe communication through which fluid under pressure is supplied fromthe brake pipe I to the auxiliary reservoir (not shown) and to the emergency reservoir 4. In addition, the service portion operates to supplyfluid under pressure from the auxiliary reservoir to the brake cylinder2 until the pressure of the fluid in the auxiliary reservoir is reducedsubstantially to the pressure at which the pressure in the brake pipe isreduced.

On a reduction in the pressure of the fluid in the brake pipe at aservice rate, fluid under pressure flows from the valve chamber I6 andthe pressure chamber IT to the chamber !2 on the face of the piston I0by way of the passage I08 to the chamber I06 and thence past the seatrib IIO to the chamber H2 from which the fluid flows by way of thepassage I54 to the chamber I52 outwardly of the seat rib I36. At thistime the diaphragm I34 is held away from the seat rib I36 by the fluidunder pressure in the chambers I44 and I52 on opposite sides of the seatrib I36, so that fluid under pressure will flow from the chamber I52past the seat rib I36 to the chamber I44 within the seat rib I36 andthence by way of the passage I48 and through the choke I50 to thechamber I2 on the face of the piston I0.

The choke I50 is proportioned to permit fluid under pressure to flowfrom the chambers I6 and I! at a rate Which enables the pressure of thefluid in the chambers I6 and IT tobe reduced substantially as rapidly asthe pressure of the fluid in the chamber I2 on the face of the piston I0is reduced during a reduction in brake pipe pressure at a service rate.

As the pressure of the fluid in the chambers I6 and I! is reduced by theflow of fluid therefrom to the brake pipe substantially as rapidly asthe pressure of the fluid in the chamber I2 is reduced during areduction in the pressure of the fluid in the brake pipe at a servicerate, no differential will be developed in the pressure of the fluid inthe chambers on opposite sides of the piston I0, and the piston I0 will,therefore, remain in the normal release position. 7

The pressure of the fluid in the brake pipe will not be reduced toatmosphere during a service application of the brakes, but will bemaintained at a substantial value. The fluid under pressure in thechambers I44 and I52 on the face of the diaphragm I34 will be at thepressure of the fluid in the brake pipe, and this pressure is exertedover the entire face of the diaphragm I34 and is sufiicient to overcomethe opposing force of the spring I38 and maintain the diaphragm I34 awayfrom the seat rib I36.

Since the diaphragm II6 of the valve device I20 is subject to theopposing pressures of the fluid in the chambers I06 and H8, whichcommunicate with the valve chamber I6 and the brake pipe respectively,the valve I04 will be held away from the seat rib I I0 by the spring II4during a service reduction in brake pipe pressure, because as justdescribed, the fluid pressure in the valve chamber I6 is reduced atsubstantially the same rate as the brake pipe pressure is reduced.

On a subsequent increase in the pressure of the fluid in the brake pipeto effect the release of the brakes, the service portion (not shown) ofthe brake controlling valve device 5 operates as described in detail inthe above identified patent to release fluid under pressure from thebrake cylinder 2 and to open a communication through which fluid underpressure is supplied from the brake pipe to the auxiliary reservoir (notshown) and to the emergency reservoir 4.

On this increase in the pressure of the fluid in the brake pipe therewill be a similar increase in the pressure of the fluid in the chamberI2 on the face of the piston I0, and fluid under pressure will flowtherefrom through the choke I50 to the passage I48 and therethrough tothe chamber I44 on the face of the diaphragm I34 of the valve means I32.Fluid under pressure supplied to the chamber I 44 will flow therefrom byway of the passage I46 to the chamber I I8 on the face of the diaphragmII6 to increase the pressure of the fluid in this chamber.

Fluid under pressure supplied to the chamber I44 flows past the seat ribI36 to the chamber I52 and therefrom through the passage I54 to thechamber H2 and thence past the seat rib IIO to the chamber I06. Fluidunder pressure supplied to the chamber I06 flows therefrom by way of thepassage I08 to the valve chamber I6 and to the pressure chamber H toincrease the pressure of the fluid in these chambers, while there willbe a similar increase in the pressure of the fluid in the chamber I06 onthe face of the diaphragm II6.

In addition, fluid under pressure supplied to the passage I54 will flowthrough the passage I56 and through the choke I58 to the passage I08leading to the chambers I6 and IT.

The rate of increase in the pressure of the fluid in the brake pipe Iand the chamber I2 on the face of the piston I0 during the release ofthe brakes after a service application of the brakes, and the rate offlow of fluid under pressure from the chamber I2 through the choke I50to the chambers I6 and I1 are such that during normal operation of thebrake equipment the pressure of the fluid in the chambers I6 and I! willbe increased substantially as rapidly as the pressure of the fluid inthe chamber I2 is increased. As a result the differential between thepressure of the fluid in the chambers on opposite sides of the piston I0during this increase in the pressure of the fluid in the brake pipe willbe relatively small and the force exerted on the piston I0 by the fluidunder pressure in the chamber I2 will not exceed the opposing forceexerted on the piston I0 by the fluid under pressure in the chamber I6by an amount suflicient to move the piston I0 against the spring 36. Thepiston I0. therefore, will not be moved to the inner release position,but will remain in the normal release position.

Fluid under pressure supplied to the chamber I44 will flow past the seatrib I36 to the chamber I 52 and therefrom by way of the passage I54 tothe chamber I I2 from which it will flow past the seat rib H0 at a rapidrate to the chamber I06 and thence by way of the passage I08 to thechambers I6 and I1.

As fluid under pressure is supplied from the chamber I44 to the chambersI06 and the chambers I6 and IT at a rapid rate the pressure of the fluidin the chamber I06 will be increased substantially as rapidly as thepressure of the fluid in the chamber H8 is increased by the flow offluid thereto from the chamber I44 by way of the passage I46.

As pressures in the chambers I06 and H6 on opposite sides of thediaphragm II6 of the valve device I02 are substantially equal,substantially no force will be exerted on the diaphragm I I6 and tendingto move the valve I04 against the spring I I4 into engagement with theseat rib I I0. As a result, therefore, the spring I I4 will maintain thevalve I04 away from the seat rib I I0 so as to permit fluid underpressure to flow from the chamber I I 2 to the chamber I06 at a rapidrate, and therefrom by way of the passage I08 to the chambers I6 and II.

On a reduction in the pressure of the fluid in the brake pipe I at anemergency rate to effect an emergency application of the brakes, theservice portion (not shown) of the brake controlling valve device 5operates as described in detail in the above identified patent to closethe communication through which fluid under pressure is supplied fromthe brake pipe I to the auxiliary reservoir (not shown) and to theemergency reservoir 4, and to supply fluid under pressure from theauxiliary reservoir (not shown) to the brake cylinder 2. I

When the brake pipe pressure is reduced at an emergency rate, there willbe a back flow of fluid from the valve chamber I6 to the brake pipe byway of the passage I48 and the choke I58, as in a service reduction inbrake pipe pressure, but since the brake pipe pressure is now beingreduced at an emergency rate, the pressure on the brake pipe side of thepiston ID will reduce more rapidly than the pressure in the valvechamber I6 can reduce by flow through the restricted port I50, and as aresult, a differential pressure is created in the valve chamber I6 whichcauses the piston I6 to be shifted relative to the main slide valve I8against the opposing force of the spring 26 acting through the plunger24.

On this movement of the piston I0 and the stem 22 the auxiliary slidevalve 29 is moved relative to the main slide valve I8 and uncovers aport I56 through the main slide valve I8 which communicates with thepassage 88 leading to the chamber I8 on the face of the vent valvepiston I6. When the auxiliary slide valve 20 is moved to a position touncover the port I56 through the main slide valve I8 fluid underpressure from the chamber I6 flows through the port I56 to the passage86 and therethrough to the chamber I8 on the face of the vent valvepiston I6. The rate of flow of fluid under pressure through the passageto the chamber I8 is substantially more rapid than the rate at whichfluid under pressure may escape from the chamber I8 through the groove84 around the piston I6 and through the choke 88 in the passage 86. As aresult there will be a rapid increase in the pressure of the fluid inthe chamber I8 and the vent valve piston I6 will be moved to the right,as viewed in the drawings, and this movement of the piston I6 will betransmitted through the stem 94 to move the vent valve 96 away from theseat rib 98 against the opposing force of the spring I60 and of thefluid under pressure in the chamber 91.

On this movement of the piston I6 the face of the piston is moved intoengagement with the seat rib 92 on the gasket 98 so as to prevent theescape of fluid under pressure from the chamber I8 around the peripheryof the piston.

On movement of the vent valve 96 away from the seat rib 98 a relativelylarge opening is provided through which fluid under pressure suppliedfrom the brake pipe I by way of the branch pipe I4, and the passages I3,62 and 99 to the chamber 9! may escape to the atmosphere by way of theatmospheric passage 82. There will, therefore, be a rapid reduction inthe pressure of the fluid in the brake pipe, and also in the chamber I2on the face of the piston II], as this chamber communicates with thepassage I3.

On this sudden reduction. in the pressure of the fluid in the chamber I2there will be rapid decrease in the force exerted on the piston I9 andopposing movement of this piston by the fluid under pressure in thechamber I6, and the piston I0 and the stem 22 will thereafter be movedto the right, as viewed in the drawings, very rapidly by the fluid underpressure in the chamber I6.

The piston I8 and the stem 22 are moved to the right, as viewed in thedrawings, until the face of the piston engages the face of the gasketI68 which is clamped between the emergency portion 8 and the pipebracket section I. This is the emergency application position of thepiston III.

On movement of the piston I 8 and the stem 22 a short distance towardsthe application position a shoulder 558 on the piston stem 22 engagesthe end of the main slide valve I 8 so that on further movement of thepiston I0 and the stem 22 towards the application position the mainslide valve I8 is moved upon its seat and uncovers the end of thepassage 86 so as to permit fluid under pressure in the chamber I6 tocontinue to flow to the passage 89 and therethrough to the chamber I8 onthe face of the vent valve piston I6.

Upon movement of the piston I9 to emergency position, the main slidevalve I8 is moved so that a cavity I62 therein establishes communicationbetween a port in the seat of the slide valve to which is connected thepassage 44 leading from the emergency reservoir 4, and a passage I64leading to the brake cylinder 2, so that fluid under pressure will nowflow from the emergency reservoir 4 to the brake cylinder 2.

Fluid under pressure supplied to the chamber I8 at the face of the ventvalve piston 76 will be vented therefrom at a restricted rate throughthe choke 88 and the passage 86 through the piston I6. The volume of thechambers I6 and I! and the rate of flow of fluid under pressure throughthe choke 88 are proportioned so as to maintain the pressure of thefluid in the chamber I8 at a value suflicient to hold the piston I6inengagement with the seat rib 92 against the opposing force of thespring I 99, and thereby hold the vent valve 96 away from the seat rib98, until the pressure of the fluid in the brake pipe I has been reducedto atmospheric pressure or substantially to atmospheric pressure.

When the pressure of the fluid in the chamber 18 has been reduced to arelatively low value by the venting of fluid under pressure therefromthrough the choke B8 and passage 86, the force exerted by this fluid onthe piston I6 is insufficient to maintain this piston against theopposing force of the spring I88 acting through the Vent valve 96 andthe stem 94, and the spring I88 will thereupon move the vent valve9linto engagement with the seat rib 98, while the piston I6 will bemoved away from the seat rib 92 to the position in which it is shown inthe drawings, in which position the groove 84 extends around the piston16. When the piston I6 is moved to this position any fluid underpressure remaining in the chambers I6 and I1 and in the chamber F8 onthe face of the piston I6 can escape therefrom at a rapid rate throughthe groove 64 around the piston I6 and thence to the atmosphere by wayof the passage 82. The chambers I6 and I1, therefore, will be reducedsubstantially to atmospheric pressure.

On movement of the piston I9 to the application position the passage M8is in communication with the chambers I6 and I1, and on a reduction inthe pressure of the fluid in these chambers to atmospheric pressure thefluid in the chambers I44 and I 52 on the face of the diaphragm I34 ofthe valve means !32 will be reduced to a mospheric pressure, and thedia-- phragm I34 will be moved into engagement with the seat rib I36 bythe spring I38.

In addition, when the pressure of fluid in the chambers l6 and I1 isreduced to atmospheric pressure the fluid in the chambers I66 and H8 onopposite sides of the diaphragm H6 will be at atmospheric pressure also,and as the pressure on the opposite sides of the diaphragm H6 is equal,the valve I64 will be held away from the seat rib H6 by the spring H4,while the diaphragm H6 will be held in engagement with the stops orprojections I29.

On a subsequent increase in the pressure of the fluid in the brake pipeI to eifect the release of the brakes, fluid under pressure flowstherefrom by way of the branch pipe I4 to the passage I3 and to thechamber I2 on the face of the piston I6. When the pressure of the fluidin the chamber I2 has increased to a predetermined relatively low valuethe force exerted by this fluid under pressure on the piston I6,together with the force exerted by the spring 26 acting through thepiston stem 22, is sufficient to cause the piston III to move away fromthe gasket I66. On this movement of the piston I6 the piston, the stem22 and the auxiliary slide valve 26 are moved relative to the main slidevalve I8 and the auxiliary slide valve 26 is moved to a position tocover the end of the passage I56 through the main slide valve I8.

On a further increase in the pressure of the fluid in the chamber I2 onthe face of the piston iii, the piston I6 is moved farther to the left,as viewed in the drawings, and on this movement of the piston I6 themain slide valve I8 is moved upon its seat and is moved to a position inwhich the cavity I62 therein no longer establishes communication betweenthe passage 44 leading from the emergency reservoir 4, and the passageI64 leading to the brake cylinder 2. so that communication between theemergency reservoir 4 and the brake cylinder 2 is cut off.

In addition on this movement of the main slide valve IS the end of theslide valve covers the end of the passage 86 to cut off communicationbetween the valve chamber I6 and the passage 86, while the slide valveI8 is moved to a position in which the port I56 through the slide valvecommunicates with the passage 86.

After a certain amount of movement of the piston I6 it will be moved toa position to open communication between the chamber I2 and the portthrough which fluid under pressure is supplied from the chamber I2through the choke I56 to the passage I48 leading to the chamber I44 onthe face of the diaphragm I34 of the valve means I32. Fluid underpressure supplied to the chamber I44 will flow therefrom through thepassage. I-ifi to the chamber H8 on the face of the diaphragm H6, and.on a predetermined increase in the pressure of the fluid in the chamberH8 the diaphragm H6 will be forced upwardly and its movement will betransmitted through the plunger I26 and the spring I26 to the springseat I22 and through the stem I24 to the valve I64 to move this valveinto engagement with the seat rib H6 against the spring Fluid underpressure supplied from. the brake pipe through passage I48 acts on thearea of the diaphragm I34 within the seat rib I36, and when the brakepipe pressure has been increased to a predetermined degree sufficient toovercome the pressure of spring I38, the diaphragm I34 will be movedfrom its seat so as to open communication from the brake pipe to thevalve chamber I5 by way of the restricted port I58.

Since fluid under pressure cannot flow from the brake pipe to the valvechamber I6 until the diaphragm I34 is unseated, and as the pressure inthe brake pipe must be increased to a substantial value before thediaphragm I34 is unseated, it will be seen that a diiferential pres sureis built up in the brake pipe which insures movement of the piston I6 tofully open the port leading from the chamber I2 to the choke I56 and thepassage I48.

The choke IE6 is of much smaller flow capacity than the choke I56 and isproportioned so as to permit fluid to flow therethrough only at arelatively slow rate, and as a result, there will be a relatively slowincrease in the pressure of the fluid in the chambers I6 and I? and I66.

During the release of the brakes after an emergency application of thebrakes, the pressure of the fluid in the brake pipe I will be increasedat a relatively rapid rate and there will be a corresponding rapidincrease in the pressure of the fluid in the chamber I2. As the pressureof the fluid in the chamber I2 on the face of the piston I6 increases ata relatively rapid rate, and as the pressure of the fluid in the chamberI6 on the opposite face of the piston I6 can only increase at arelatively slow rate because of the restricted rate of flow of fluidunder pressure through the choke I58, there will be a graduallyincreasing differential between the pressure of the fluid in. thechamber 52 and the pressure of the fluid in the chamber I6.

As a result there will be a corresponding gradual increase in the forcetending to move the piston I0 to the left, and when the differencebetween the pressures of the fluid in the chambers I2 and I6 increasesto a predetermined value, the force exerted on the piston I!) by the.

fluid under pressure in the chamber I2 will exceed the opposing forceexerted by the fluid under pressure in the chamber I6 on the oppositeface of the piston I6 by an amount sufficient to move the piston I6against the opposing force of the,-

spring 36 acting through the plunger 36.

The piston III will thereupon. be moved from the normal release positionto the inner release position against the spring 36 and will move themain slide valve I8 to a position in which the;

of the fluid in the chamber within the seat rib:

68, the accelerated release check valve 64 will be moved away from theseat rib 68 against the opposing force of the spring 66 and of the fluidunder pressure in the chamber 66, which at this time will be at arelatively low value, and fluid under pressure will flow to the chamber60 and thence by way of the passage 62 to the passage I3, whichcommunicates with the chamber I2 on the face of the piston I6, and withthe branch pipe I4 leading to the brake pipe I so as to increase thepressure of the fluid in the brake pipe and in the chamber I2.

When the pressure of the fluid in the brake cylinder 2 and the auxiliaryreservoir (not shown) and in the brake pipe I have substantiallyequalized by the flow of fluid under pressure from the brake cylinderand the auxiliary reservoir to the brake pipe the accelerated releasecheck valve 64 is moved into engagement with the seat rib 00 by thespring 66 so as tocut off the further flow of fluid under pressure fromthe brake cylinder to the brake pipe, and to prevent back flow of fluidunder pressure from the brake pipe I to the brakecylinder 2.

During the time that the piston I0 and the main slide valve I8 are inthe inner release position fluid under pressure continues to flow fromthe chamber I2 through the choke I58 to the chambers I6 and I1, andafter a time interval the pressure of the fluid in the chambers I6 andI7 will have increased to a value such that the force exerted on thepiston I0 by the fluid under pressure in the chamber I6, together withthe force exerted by the spring 36 acting through the plunger 30, issufficient to overcome the opposing force exerted on the piston I0 bythe fluid under pressure in, the chamber I2. The piston I0 and the main,slide valve I8 will thereupon be moved by the spring 36 acting throughthe plunger 30, and by the fluid under pressure in the chamber I6 actingon the piston E0, to the right, as viewed in the drawings, from theinner release position to the normal release position. The plunger 30 isable to move the main slide valve I0 at this time as the plunger 30 isengaged by the projection 34 on the main slide valve.

When the piston I0 and the main slide valve I 8 have been moved to thenormal release position the plunger 30 engages a portion of the body ofthe emergency portion 8 which prevents further movement of the plunger30 with the result the spring 36 is no longer effective to exert forceupon the piston I0 and the stem 22, or on the main slide valve I8, andthe higher pressure of the fluid in the chamber I2 on the face of thepiston I0 prevents further movement of the piston I0 by the fluid underpressure in the valve chamber iii.

The rate of flow of fluid under pressure through the choke I58 is suchthat the pressure of the fluid in the chambers I6 and U will not haveincreased to a value suflicient to cause the piston I0 and the mainslide valve I8 to move from the inner release position to the normalrelease position until after the piston I0 and the main slide valve I8have been in the inner release position for a period of time long enoughto permit the fluid under pressure from the brake cylinder 2 and in theauxiliary reservoir to flow to the brake pipe I and substantiallyequalize the pressure of the fluid in the brake cylinder and auxiliaryreservoir and in the brake pipe.

After movement of the piston II! to the normal release position fluidunder pressure continues to flow from the chamber I2 through the chokeI59 to the passage I48 and thence to the chamber I44 from which it flowspast the seat rib I36 to the chamber I52 and therefrom by way of thepassage I54 to the passage I56 and through the choke I58 to the passageI08 leading to the chambers I 6 and H.

In addition, fluid under pressure supplied to the passage I08 flows tothe chamber I06 on one side of the diaphragm H6 of the valve device I02,while the diaphragm H6 is subject on the other side to the pressure ofthe fluid in the chamber H6. The chamber II8 is connected by way of thepassage I46 with the chamber I44 which communicates with the chamber I2and thereby with the brake pipe I through the passage I46 and the chokeI50 of relatively large flow capacity. The pressure of the fluid in thechamber H8, therefore, will be at substantially the pressure of thefluid in the chamber I2.

When the pressure of the fluid in the chamber I06 has increased to avalue such that the difference between the pressure of the fluid in thechamber I06 and in the chamber IE8 on the opposite face of the diaphragmH6 is less than a predetermined amount, the spring I26 will expand andwill move the diaphragm II6 and the plunger I20 downwardly until thespring seat I22 engages the shoulder I28 on the plunger I20. On afurther reduction in the differential between the pressure of the fluidin the chamber I06 and in the chamber H8, the spring II4 will move thevalve I04 downwardly away from the seat rib H0 and this movement of thevalve I04 will be transmitted through the spring I26 to move thediaphragm II6 into engagement with the projection I29.

After movement of the valve I04 away from the seat rib IIO fluid underpressure supplied to the passage I54 flows to the chamber H2 and thenpast the seat rib I I0 to the chamber I06 and therefrom by way of thepassage I00 to the chambers I6 and IT to increase the pressure of thefluid in these chambers at a relatively rapid rate until the pressure ofthe fluid in these chambers has equalized with the pressure of the fluidin the chamber I2 and in the brake pipe I.

If the pressure of the fluid in the valve chamber I6 increases to avalue above the pressure of the fluid in the emergency reservoir 4,fluid under pressure will flow from the valve chamber I 6 through thepassage 50 and past the ball check valve 56 to the chamber within theseat rib 54 and it will move the spill-over check valve 50 away from theseat rib 54 against the spring 52 and the pressure of the fluid in thechamber 48 so as to permit fluid under pressure to flow to the chamber48. Fluid under pressure supplied to the chamber 48 flows therefrom byway of the passage and pipe 44 to the emergency reservoir 4.

When the pressure of the fluid in the emergency reservoir 4 hasincreased substantially to the pressure of the fluid in the valvechamber I6, the spill-over check valve 50 is moved to the seatedposition by the spring 52 to cut off the flow of fluid under pressurefrom the valve chamber I6 to the emergency reservoir and to prevent backflow of fluid under pressure from the emergency reservoir 4 to the valvechamber I6.

On an increase in the pressure of the fluid the brake pipe I fluid underpressure flows therefrom by way of the branch pipe I4 to the passages inthe pipe bracket section I and to the service portion (not shown) of thebrake controlling valve device 5, and when the pressure of the fluidsupplied from the brake pipe I to the service portion has increased to avalue exceeding the pressure of the fluid in the auxiliary reservoir,the service portion operates as described in detail in the aboveidentified patent to release fluid under pressure from the brakecylinder 2 and toopen a communication through which fluid under pressuremay be supplied from the brake pipe I to the auxiliary reservoir (notshown) and to the emergency reservoir 4.

In Fig. 2 of the drawings there is illustrated a part of a brakeequipment employing a modified form of emergency portion embodying thisinvention. The emergency portion shown in Fig.

2 of the drawings is identical in construction and operation with theemergency portion shown in Fig. l of the drawings, except in certainparticulars, as will hereinafter be described in detail, and identicalreference numerals are employed for the emergency portion and otherparts of the brake equipment shown in Fig. 2 of the drawings to identifythe portions of the equipment which are also employed in the brakeequipment shown in Fig. 1 of the drawings.

The emergency portion 8a shown in Fig. 2 of the drawings differs fromthe emergency portion 8 shown in Fig. 1 of the drawings in theconstruction of the valve means I32a, which controls the flow of fluidfrom the brake pipe to the chambers I6 and I1. As shown in Fig. 2 of thedrawings, this valve means comprises a movable abutment in the form of adiaphragm I34a, which is yieldingly held in engagement with a seat ribI36 by means of a spring I38a acting through a plunger I62 carried bythe diaphragm. The spring [38a is substantially stronger than thecorresponding spring I36 employed in the emergency portion shown in Fig.1 of the draw ings. The spring I38a is mounted in a chamber I4Ila, whichis constantly connected to the atmosphere through a choke I64.

The plunger I62 is hollow and has mounted therein a spring I66, whichextends between the plunger and a flange I68 on a valve I16, which isadapted to engage a seat surrounding the end of a passage I12, whichcommunicates with the passage I54, and thereby through the choke I58with the valve chamber I6 and the pressure chamber I1. The flange IE8 isadapted to engage an inwardly extending flange I14 on the plunger I62 tolimit movement of the valve I10 by the spring I66.

The diaphragm I34a has secured on the other face thereof a plunger I16,which extends into the chamber I44 within the seat rib I36. The plungerI16 is hollow and has mounted therein a spring I18 which extends betweenthe plunger and a valve I62, which is adapted to engage a seatsurrounding the end of a passage I84 leading from the chamber 66 inwhich the accelerated release check valve 64 is mounted. The valve I82carries a radially outwardly extending flange I86 which is adapted toengage an inwardly extending flange I86 on the plunger I16 to limitmovement of the valve I82 by the spring I18.

The emergency portion 8a is shown in the drawings in the position whichit assumes when the brake equipment is at atmospheric pressure, and withthe piston I6 in the normal release position. At this time the diaphragmI I6 of the Valve device I02 is held in engagement with the projections!29, while the valve I64 is held away from the seat rib H6 by the springII4.

In addition, at this time the diaphragm l34a of the valve means I32a. isheld in engagement with the seat rib !36 by the spring 138a, while thevalve I32 is held in the seated position by the spring I18.

When the diaphragm I34a is in engagement with the seat rib E36, thevalve I18 is held away from its seat so that the valve chamber I6 isconnected to the atmosphere by way of the passage I68, choke I58,passages I56, I54 and I12, the chamber Mile, and the choke I64.

In initially charging the equipment fluid under pressure is supplied tothe brake pipe I, and it flows therefrom through the branch pipe I4 tothe passage i3 in the pipe bracket section 1, and to the chamber I2 onthe face of the piston I0.

Fluid under pressure supplied to the passage I3 also flows to theservice portion, not shown, of the brake controlling valve device a andcauses the piston of this portion to move to the release position inwhich the brake cylinder 2 is connected to the atmosphere, and in whicha communication is opened through which fluid under pressure may flowfrom the passage I3 to the auxiliary reservoir, not shown, and to theemergency reservoir 4 to charge these reservoirs with fluid underpressure.

Fluid under pressure supplied by the service portion of the brakecontrolling valve device 5a to the emergency reservoir 4 flows by way ofthe passage 44 to the chamber 42 on the face of the diaphragm 40, andincreases the force ex erted through the stem 38 to maintain the mainslide valve I8 in engagement with its seat.

Fluid under pressure supplied from the brake pipe l to the passage I3flows to the chamber I2 on the face of the piston II) of the emergencyportion 8a and increases the pressure of the fluid in this chamber. Onan increase in the pressure of the fluid in the chamber I2 the piston I6will be moved to the left, as viewed in Fig. 2 of the drawings, to thenormal release position, if it is not already in that position, which isthe position in which it is shown in this figure of the drawings. Onmovement of the piston ID to the normal release position communicationis opened between the chamber I2 and the passage I48 through the chokeI50 to the chamber I44 on the face of the diaphragm I34a, which at thistime is held in engagement with the seat rib I36 by the spring I38a.

The spring I38a of such value, and the chamber E44 within the seat ribI36 is of such area, that the diaphragm I34a is held in engagement withthe seat rib I36 until the pressure of the fluid in the chamber I44within the seat rib I36 has increased to a relatively high predeterminedvalue.

On the supp-1y of fluid under pressure to the chamber I44, fluid underpressure flows therefrom by way of the passage I46 to the chamber IIB onthe face of the diaphragm II6 of the valve device I62.

On a predetermined increase in the pressure of the fluid in the chamberII8, the diaphragm I I6 is moved upwardly, as viewed in the drawings,thereby moving the plunger I26 upwardly, and this movement of theplunger is transmitted through the spring I26 to the spring seat I22 topress the stem I24 against the valve I64 and thereby move this valveagainst the spring II4 into engagement with the seat rib I ID.

The increase in the pressure of the fluid in the chamber I44 will beaccompanied by a similar increase in the pressure of the fluid in thechamber I2 on the face of the piston I6, and the fluid under pressure inthis chamber exerts a force on the piston I0 tending to move it to theleft, as viewed in Fig. 2 of the drawings. Movement of the piston I6further to the left, as viewed in the drawings, from the normal releaseposition to the inner release position is resisted by the spring 36acting through the plunger 30, which is engaged by the shoulder 32 onthe piston stem 22 and by the projection 34 on the main slide valve I8.The various parts of the emergency valve portion shown in this figure ofthe drawings, like that shown in Fig. 1 of the drawings, are arranged sothat the spring 36 and the plunger 36 are not effective to opposemovement of the piston ID in this direction until the piston II] hasbeen moved to a position to completely open the port through which thepassage I48 com municates with the chamber I 2 on the face of the pistonI6.

When the pressure of the fluid in the chamber I2 has built up to arelatively high value it exerts suflicient force on the piston In tocause it to move against the spring 36 to theinner release position. Ifduring the period in which the pressure of the fluid in the chamber i2is being increased, any fluid under pressure should leak past the pistonI6, and the packing ring H carried thereby, to the valve chamber I6, itwill escape to the atmosphere by way of the passage I68, choke I58,passages I56, I54 and I12, and the valve means I32a.

The spring I38a, and the other portions of the valve means I32a, arearranged and proportioned so that the diaphragm I34a. is held inengagement with the seat rib I36 until the pressure of the fluid in thechamber I44 within the seat rib I36, and therefore in the chamber I2 onthe face of the piston I6, has increased to a value somewhat higher thanis required to effect movement of the piston I6 against the spring 36 tothe inner release position. As a result, no fluid under pressure will besupplied to the valve chamber I6 until after the piston I0 has beenmoved. to the inner release position.

On an increase in the pressure of the fluid in the chamber I44 to asomewhat higher value than is required to effect movement of the pistonI6 to the inner release position, the force exerted by the fluid underpressure in the chamber I44 on the area of the diaphragm I34a within theseat rib I36 is suflicient to overcome the opposing force of the springI38a, and the diaphragm I34a will thereupon be moved upwardly, as viewedin Fig. 2 of the drawings, away from the seat rib I 36.

As soon as the diaphragm 134a is moved away from the seat rib I36, fluidunder pressure flows from the chamber I44 within the seat rib I36, tothe chamber '12 outwardly thereof so that the entire face of thediaphragm I 34a is subject to fluid under pressure. As a result of thisincrease in the area of the diaphragm I34a which is subject to fluidunder pressure, there will be a substantial increase in the forceexerted on the diaphragm I34a as soon as it is moved away from the seatrib I36, and it will thereafter be moved against the spring I38a veryrapidly.

After a slight amount of upward movement of the diaphragm I34a, theinwardly extending flange I86 on the plunger I16 engages the flange I66on the valve I82 so that upon further upward movement of the diaphragml34a, the valve I62 is lifted away from the seat surrounding the end ofthe passage I84.

As soon as the valve I82 is lifted away from its seat fluid underpressure may flow from the chamber I44 through the passage I84 to thechamber 66 in which the accelerated release check valve 64 is mounted.At this time the accelerated release check valve 64 is held in theseated position by the spring 66 soas to prevent the flow oi fluid fromthe chamber '66 tothe chamber within the seat rib 68 and therefrom tothe passage 12.

On a slight further upward movement of the diaphragm I34a, the valve I10is moved to'the seated position so as to cut off communication betweenthe passage I12 and the chamber I 40a. On further upward movement of thediaphragm I341; subsequent to movement of the valve I16 into engagementwith its seat, the spring I66 is compressed and the plunger I62 is movedrelative to the Valve I16 until further movement of the diaphragm I34ais prevented by engagement of a portion of the plunger I62 with aportion of the body of the emergency portion Ba.

On movement of the diaphragm I34a away from the seat rib I36, and on thesupply of fluid under pressure from the chamber I44 Within the seat ribI36 to the chamber I52 outwardly thereof, fluid under pressure flowsfrom the chamber I52 through the passage I54 to the chamber II2 withinthe seat rib I I6 of the valve device I62. As the valve I64 is held inengagement with the seat rib H6 at this time, fluid under pressure willnot flow from the chamber II2 to the chamber I66 in the valve deviceI62.

Fluid under pressure supplied to the passage I54 also flows to thepassage I12, but as the valve I16 has been moved to the seated position,fluid under pressure will not flow from the passage I12 to the chambermm, from which it could escape to the atmosphere by Way of the chokeI64.

Fluid under pressure supplied to the passage I54 also flows therefrom tothe passage I56, and through the choke I58 to the passage I68, throughwhich it flows to the chamber I66 in the valve device I62, and to thevalve chamber I6 and the pressure chamber I1 to increase the pressure ofthe fluid in these chambers. The choke I58 restricts the rate of flow offluid to these chambers, and, as a result, there will be a slow rate ofincrease in the pressure of the fluid in these chambers.

After a time interval the pressure of the fluid in the valve chamber I6will have increased to a value such that the force exerted on the pistonI6 by this fluid under pressure, together with the force exerted by thespring 36, is sufficient to overcome the opposing force of the fluidunder pressure in the chamber I2, and the piston I6 and the main slidevalve I8 Will thereupon be moved to the right, asv viewed in Fig. 2 ofthe drawings, from the inner release position towards the normal releaseposition. After a certain amount of shown in Fig. 1 of the drawings, arearranged 5 and proportioned so that the plunger 36 engages a portion ofthe body of the emergency portion before the piston I6 has been moved toa position to restrict the rate of flow of fluid from the chamber I2through the choke I56 to the passage I48.

After movement of the piston II) from the inner release position to thenormal release position, the pressure of the fluid in the valve chamberI6 continues to increase by the flow of fluid thereto from the chamberI2 through the choke I58 until the pressure of the fluid in the valvechamber I6 has substantially equalized with the pressure of the fluid inthe chamber I2 on the opposite side of the piston l6.

On an increase in the pressure of the fluid in the valve chamber I6,there is a corresponding increase in the pressure of the fluid in thechamber I66 of the valve device I62. When the pressure of the fluid inthe chamber I66 has increased approximately to the pressure of the fluidin the brake pipe, and consequently in the chamber II 8 on the oppositeface of the diaphragm I6, the force exerted by the fluid under pressurein the chamber I05, supplemented by the force exerted by the spring I2'6acting through the plunger I20, will be suflicient to overcome theopposing force of the fluid under pressure in the chamber H8, and thediaphragm II6 will be moved downwardly, as viewed in Fig. 2 of thedrawings, thereby permitting the spring I26 to expand.

The spring I26 will expand until the spring seat I22 engages theinwardly extending flange I28 on the plunger I20, and will thereafter beineffective to exert force on the diaphragm II6 tending to move thediaphragm against the opposing force of the fluid under pressure in thechamber II8.

However, the spring I I4 is now effective to assist movement of thediaphragm II6 against the opposing force of the fluid under pressure inthe chamber Il8, but the spring H4 is substantially weaker than thespring I26 and exerts substantially less force than the spring I26exerted.

On a slight further increase in the pressure of the fluid in the chamberI06, which is at substantially the same pressure as the fluid in thecham bers I6 and II, the force exerted by the fluid under pressure inthe chamber I06, supplemented by the force exerted by the spring II4acting through the valve I04 and the spring I26, will be suflicient tomove the diaphragm II6 against the opposing force of the fluid underpressure in the chamber H8, and the diaphragm II6 will thereupon bemoved downwardly into engagement with the projections I29, while thevalve I04 will be moved away from the seat rib IIO by the spring II4 soas to, permit fluid under pressure to flow from the chamber II2 to thechamber I06 at a rapid rate.

Fluid under pressure can now flow from the brake pipe to the valvechamber I6 and the pressure chamber I'I past the valve I04, as well asthrough the choke I58, so that the further charging of the valve chamberand the pressure chamber occurs at a rapid rate.

Upon a subsequent reduction in the pressure of the fluid in brake pipe Iat a service rate to effect a service application of the brakes, theservice portion, not shown, of the brake controlling valve device 5aoperates, as described in detail in the above identified patent, toclose the communication through which fluid under pressure is suppliedfrom the brake pipe to the auxiliary reservoir, not shown, and to theemergency reservoir 4. In addition, the service portion operates tosupply fluid under pressure from the auxiliary reservoir to the brakecylinder 2 until the pressure of the fluid in the auxiliary reservoir isreduced substantially to the pressure at which the pressure in the brakepipe is reduced.

On a reduction in the pressure of the fluid in the brake pipe at aservice rate, fluid under pressure flows from the valve chamber I6 andthe pressure chamber H to the chamber I2 on the face of the piston I0,by way of the passage I08 to the chamber I06, and thence past the valveI04 to the chamber II2, from which the fluid flows by way of the passageI54 to the chamber I52 outwardly of the seat rib I36. At this time thediaphragm I34a is held away from the seat rib I36 by the fluid underpressure in the chambers I44 and I52 on opposite sides of the seat ribI36, so that fluid under pressure will flow from the chamber I52 pastthe seat rib I36 to the chamber I44 within the seat rib I36, and thenceby way of the passage I48 and through the choke I50 to the chamber II2on the face of the piston I0.

The choke I50 is proportioned to permit fluid under pressure to flowfrom the chambers I6 and I! at a rate which enables the pressure of thefluid in the chambers I6 and I! to be reduced substantially as rapidlyas the pressure of the fluid in the chamber I2 on the face of the pistonI is reduced during a reduction in brake pipe pressure at a servicerate.

As the pressure of the fluid in the chambers I6 and I1 is reduced by theflow of fluid therefrom to the brake pipe substantially as rapidly asthe pressure of the fluid in the chamber I2 is reduced during areduction in the pressure of the fluid in the brake pipe at a servicerate, no differential will be developed in the pressure of the fluid inthe chambers on opposite sides of the piston I0, and the piston I0,therefore, will remain in the normal release position.

During a service application of the brakes the pressure of the fluid inthe brake pipe is maintained at a substantial value, and the fluid underpressure in the chambers I44 and I52 acting on the face of the diaphragmI34awill maintain. the diaphragm I34a away from the seat rib E35 againstthe opposing force of the spring I36a, while the valve I10 is held inthe seated position.

Since the diaphragm I I6 of the valve device I02 is subject to theopposing pressures of the fluid in the chambers I06 and I I8, whichcommunicate with the valve chamber I6 and the brake pipe I,respectively, the valve I04 will be held away from the seat rib I I0 bythe spring I I4 during a service reduction in brake pipe pressure,because, as just described, the fluid pressure in the valve chamber I6is reduced at substantially the same rate as the brake pipe pressure isreduced.

On a subsequent increase in the pressure of the fluid in the brake pipeto effect the release of the brakes, the service portion not shown, ofthe brake controlling valve device 5a operates, as described in detailin the above identified patent, to release fluid under pressure from thebrake cylinder 2, and to open a communication through which fluid underpressure is supplied from the brake pipe I to the auxiliary reservoir,not shown, and to the emergency reservoir 4.

On this increase in the pressure of the fluid in the brake pipe therewill be a similar increase in the pressure of the fluid in the chamberI2 on the face of the piston I0, and fluid under pressure will flowtherefrom through the choke I50 to the passage I48, and therethrough tothe chamber I44 on the face of the diaphragm I3 ia of the valve meansI32a. Fluid under pressure supplied to the chamber I44 will flowtherefrom by way of the passage I46 to the chamber I I8 on the face ofthe diaphragm H6 to increase the pressure of the fluid in this chamber.

Fluid under pressure supplied to the chamber I44 also flows past theseat rib I36 to the chamber I52 and therefrom through the passage 554 tothe chamber H2, and thence past the valve I04 to the chamber I06. Fluidunder pressure supplied to the chamber I06 flows therefrom by way of thepassage I08 to the valve chamber I6 and the pressure chamber I! toincrease the pressure of the fluid in these chambers, while there willbe a similar increase in the pressure of the fluid in the chamber I06 onthe face of the diaphragm H6.

In addition, fluid under pressure supplied to The rate of increase inthe pressure of the fluid in the brake pipe I and in the chamber I2 onthe face of the piston I6 during the release of the brakes after aservice application of the brakes, and the rate of flow of fluid underpressure from the chamber I2 through the choke I58 to the chambers I6and I! are such that during normal operation of the brake equipment, thepressure of the fluid in the chambers I6 and I! will be increasedsubstantially as rapidly as the pressure of the fluid in the chamber I2is in creased. As a result no differential between the pressure of thefluid in the chambers on opposite sides of the piston H3 will bedeveloped during this increase in the pressure of the fluid in the brakepipe, and no force will be exerted on the piston I 0 by the fluid underpressure in the chamber It to move the piston I6 against the spring 35.The piston I ll, therefore, will remain in the normal release position,and will not be moved to the inner release position.

During this increase in the pressure of the fluid in the valve chamberI6 there will be a similar rapid increase in the pressure of the fluidin the chamber E66 of the valve device I62, and as the pressure of thefluid in this chamber is increased substantially as rapidly as thepressure of the fluid in the chamber IIB on the opposite face of thediaphragm II6, which chamber is at substantially the pressure of thefluid in the chamber I2, substantially no force will be exerted on thediaphragm H6 and tending to move the valve I64 against the spring II4into engagement with the seat rib I I0. As a result, therefore, thespring I I4 will maintain the valve I04 away from the seat rib IIEi soas to permit fluid under pressure to flow from the chamber IIZ to thechamber Hi5, and therefrom by way of the passage I08 to the chambers I6and I1.

On a reduction in the pressure of the fluid in the brake pipe I at anemergency rate to effect an emergency application of the brakes, theservice portion, not shown, of the brake controlling valve device 5aoperates, as described in detail in the above identified patent, toclose the communication through which fluid under pressure is suppliedfrom the brake pipe I to the auxiliary reservoir, not shown, and to theemergency reservoir and to supply fluid under pressure from theauxiliary reservoir to the brake cylinder 2.

When the brake pipe pressure is reduced at an emergency rate, there willbe a back flow of fluid from the valve chamber It to the brake pipe byway of the passage I48 and choke I50, as in a service reduction in thebrake pipe pressure, but since the brake pipe pressure is now beingreduced at an emergency rate, the pressure on the brake pipe side of thepiston It! will reduce more rapidly than the pressure in the valvechamber MS can reduce by flow through the restricted port E553, and, asresult, a differential pressure is created in the valve chamber I6 whichcauses the piston I6 and the auxiliary slide valve 2G to be shiftedrelative to the main slide valve I8 against the opposing force of thespring 26 acting through the plunger 24.

On this movement of the piston I6 and the stem 22 the auxiliary slidevalve 20 is moved rela tive to the main slide valve I8 so as to uncovera port I56 through the main slide valve I8, which communicates with thepassage leading to the chamber 18 on the face of the vent valve pistonI6. When the auxiliary slide valve 26 is moved to the position touncover the port I56 through the main slide valve 58, fluid underpressure from the chamber I6 flows through the port I56 to the passage80, and therethrough to the chamber 78 on the face of the vent valvepiston I6. The rate of flow of fluid under pressure through the passage86 to the chamber 78 is sub stantially more rapid than the rate at whichfluid under pressure may escape from the chamber I8 through the groove84 around the piston I6, and through the choke 88 in the passage 86. Asa result, there will be a rapid increase in the pressure of the fluid inthe chamber I8, and the vent valve piston I6 will be moved to the right,as Viewed in the drawings, and this movement of the piston 16 will betransmitted through the stem 9 to move the vent valve 96 away from theseat rib 98 against the opposing force of the spring I00, and of thefluid under pressure in the chamber 9'1. On this movement of the piston56, the face of the piston is moved into engagement with the seat rib 92on the gasket so as to prevent the escape of fluid under pressure fromthe chamber I8 around the periphery of the piston 16.

On movement of the vent valve 96 away from the seat rib 98 a relativelylarge opening is provided through which fluid under pressure suppliedfrom the brake pipe by way of the branch pipe I4, and the passages I3and 99, to the chamber 91 will escape to the atmosphere by way of theatmospheric passage 82. There will, therefore, be a rapid reduction inthe pressure of the fluid in the brake pipe, and also in the chamber I2on the face of the piston I0, as this chamber communicates with thepassage I3 and the piston I0 and the stem 22 will thereafter be moved tothe right, as Viewed in the drawings, very rapid ly by fluid underpressure in the chamber I6.

The piston II] and the stem 22 are moved to the right, as viewed in thedrawings, until the face of the piston Ill engages the face of thegasket I60, which is clamped between the emergency portion 8a and thepipe bracket section I. This is the emergency application position ofthe piston II).

On movement of the piston II] and the stem 22 a short distance towardthe application position, a shoulder I58 on the piston stem 22 engagesthe main slide valve I8, so that on further movement of the piston I0and the stem 22 toward the application position, the main slide valve I8is moved upon its seat and uncovers the passage 86 so as to permit fluidunder pressure in chamber It to continue to flow to the passage 86 andtherethrough to the chamber E8 on the face of the vent valve piston l6.

Upon movement of the piston I6 to the emergency application position,the main slide valve i8 is moved so that a cavity I62 thereinestablishes communication between a port in the seat of the slide valveto which is connected the passage 44 leading from the emergencyreservoir i, and a passage I64 leading to the brake cylinder 2, so thatfluid under pressure will now flow from the emergency reservoir 4 to thebrake cylinder 2.

Fluid under pressure supplied to the chamber I8 at the face of the ventvalve piston will be vented therefrom at a restricted rate through thechoke 88 and the passage 86 through the piston I6. The volume of thechambers I6 and IT, and the rate of flow of fluid under pressure throughthe choke 88, and the other portions of this valve portion, are arrangedand proportioned so as to maintain the pressure of the fluid in thechamber I6 at a value sufficient to hold the piston I6 in engagementwith the seat rib 92 against the opposing force of the spring I00, andthereby hold the vent valve 96 away from the seat rib 88, until thepressure of the fluid in the brake pipe I is reduced substantially toatmospheric pressure.

When the pressure of the fluid in the chamber It has been reduced to arelatively low value by the venting of fluid under pressure therefromthrough the choke 88 and the passage 86, the force exerted by this fluidon the piston I6 is insufficient to maintain the piston I6 in engagementwith the seat rib 92 against the opposing force of the spring I actingthrough the vent valve 96 and the stem 94, and the spring I00 willthereupon move the vent valve 96 into engagement with the seat rib 98,while the piston I6 will be moved away from the seat rib 92 to theposition in which it is shown in the drawings, in which position thegroove 84 extends around the piston I6.

When the piston I6 is moved to this position any fluid under pressureremaining in the chambers I6 and I1, and in the chamber I8 at the faceof the piston I6, can escape therefrom at a rapid rate through thegroove 84 around the piston I6, and thence to the atmosphere by Way ofthe passage 82. The chambers I6 and II, therefore, Will be reducedsubstantially to atmospheric pressiu'e.

On movement of the piston I0 to the application position, the passageI48 is in communication with the chambers I6 and I1, so that thepressure of the fluid in the chambers I44 and I52 at the face of thediaphragm I34a reduces as the pressure of the fluid in the pressurechamber reduces, and when the pressure on the diaphragm I34a has beenreduced sufliciently the diaphragm will be moved downwardly by thespring I38a into engagement with the seat rib I36.

When the diaphragm I34a is moved into engagement with the seat rib I36,the valve I82 is pressed into engagement with its seat by forcetransmitted through the spring I'I8, while the inwardly extending flangeI'I4 on the plunger I62 engages the flange I68 on the valve I and movesP this valve away from its seat, thereby opening a communication betweenthe valve chamber I6 and the atmosphere by way of the chamber MM and hechoke I64.

The spring I38a and. the area of the diaphragm I34a subject to the fluidunder pressure are arran ed and proportioned so that the diaphragm I345:is held in its upper position by the fluid in the chambers I44 and I52,so as to maintain the valve H6 in the seated position until the pressureof the fluid in the chamber I6, and therefore in the chambers I44 andI52, has reduced to a relatively low value. As a result, there will beno venting of fluid under pressure from the valve chamber I6 through thevalve means I32a until the pressure of the fluid in the valve chamber Ithas been reduced to a relatively low value by the venting of fluidtherefrom through the vent valve piston 16.

The pressure of the fluid in the valve chamber :6 will not be reduced tothe value at which the diaphragm I34a is moved downwardly by the springI38a for a substantial time interval, so that the pressure of the fluidsupplied from the valve chamber I6 will be maintained a value greatenough to exert sufficient force on the vent valve piston I6 to maintainthe vent valve 96 open long enough to permit the fluid under pressure inthe brake pipe to reduce substantially to atmospheric pressure.

In addition, the pressure of the fluid in the chambers, I06 and H8 onopposite sides of the diaphragm II6 will reduce as the pressure in thechambers I6 and I1 reduces, and as the pressure on the opposite sides ofthe diaphragm H6 is equal, the valve I04 will be held away from the seatrib I I0 by the spring lI4, while the diaphragm I I6 will be held inengagement with the projections I29. I

On a subsequent increase in the pressure of the fluid in the brake pipeI to effect release of the brakes, fluid under pressure flows therefromby way of the branch pipe I4 to the passage I3, and to the chamber I2 onthe face of the piston I0. When the pressure of the fluid in the chamberI2 has increased to a predetermined relatively low value, the forceexerted by this fluid under pressure on the piston I0, together With theforce exerted by the spring 26 acting through the piston stem 22 issuflicicnt to cause the piston I0 to move away from the gasket I60, ifit has not already been moved away from the gasket I6 by the spring 26alone. On this movement of the piston I0, the stem 22 and the auxiliaryslide valve are moved relative to the main slide valve I8, and theauxiliary slide valve 20 is moved to a position to cover the end of thepassage I56 through the main slide valve I8.

As the piston I0 moves towards the normal release position, the mainslide valve I8 is moved to out off communication between the passages 44and I64 by way of the cavity I62, so that communication between theemergency reservoir 4 and the brake cylinder 2 is cut off.

In addition, on this movement of the main slide valve I8, the end of theslide valve covers the end of the passage 86 to out off communicationbetween the valve chamber !6 and the passage 66, while the slide valveI8 is moved to a position in which the port I56 through the slide valvecommunicates with the passage 80.

After a certain amount of movement of the piston I0, it will be moved toa position to open communication between the chamber I2 and the portthrough which fluid under pressure is sup plied from the chamber l2through the choke I50 to the passage I48 leading to the chamber I4 onthe face of the diaphragm I34a of the valve means I32a. Fluid underpressure supplied to the chamber I44 will flow therefrom through thepassage I46 to the chamber H8 on the face of the diaphragm H6, and on apredetermined increase in the pressure of the fluid in the chamber II8,the diaphragm H6 will be forced upwardly, and its movement will betransmitted through the plunger I20 and the spring I26 to the springseat I22, and through the stem I24 to the valve I04 to move this valveinto engagement with the seat rib III! against the opposing force of thespring II4.

Fluid under pressure supplied from the brake pipe I through the passageI43 to the chamber I44 acts on the area of the diaphragm I34a within theseat rib I36, tending to move the diaphragm away from the seat rib I36.However, as pointed out above, the spring I38a and the other portions ofthe valve means I32a are proportioned so that the diaphragm I34a is heldin engagement with the seat rib I36 until the pressure of the fluid inthe chamber I44, and, therefore, in the chamber I2 on the face of thepiston III, has increased to a predetermined relatively high value,which is somewhat higher than is required to eflect movement ofthe'piston Ill against the spring 36 to the inner release position.

On an increase in the pressure of the fluid in the chamber I2 on theface of the piston ID to a value somewhat less than is required to movethe diaphragm I34a against the spring I38a away from the seat rib I 36,the force exerted on the piston Ill by the fluid in the chamber I2 isgreat enough to overcome the opposing force of the spring 36, and movethe piston Ill and the main slide valve I8 from the normal releaseposition to the inner release position.

If, during the period that the pressure of the fluid in the chamber I2is increasing, and before the diaphragm I34a is moved away from the seatrib I36, any fluid under pressure should leak from the chamber I2 pastthe piston I and the packing ring II to the valve chamber I6, it willescape therefrom by way of the passage I68, the choke I58, passages I56,I54 and H2, and past the unseated valve I'IU to the chamber I40a, fromwhich it will flow to the atmosphere through the choke I64.

As means is provided to vent the valve chamber I6 during this period,there is no possibility that fluid under pressure will build up in thischamber and prevent the development of the pressure differential betweenthe chambers I2 and l6 which is necessary to move the piston Ill againstthe spring 36 from the normal release position to the inner releaseposition. The fluid under pressure in the chamber I2 will be able tomove the piston II] to the inner release position, therefore, eventhough the leakage of fluid from the chamber I2 to the valve chamber I6past the piston Ill and the packing ring II is excessive.

When the piston I6 is moved to the inner release position, the mainslide valve I8 is moved to a position in which the cavity I62 thereinestablishes communication between the passage 864 leading from the brakecylinder, and the passage I2. Fluid under pressure will thereupon flowfrom the brake cylinder 2 and the auxiliary reservoir, not shown, by wayof the pipe and passage I 64, and the cavity I62 in the main slide valveI6, to the passage I2, and through this passage past the ball checkvalve Ill to the chamber within the seat rib 68. On an increase in thepressure of the fluid in the chamber within the seat rib 68, theaccelerated check release valve 64 will be moved away from the seat rib68 against the opposing force of the spring 66, and fluid under pressurewill flow to the chamber 60. At this time, however, the valve I 82 isheld in the seated position by the diaphragm Esta acting through thespring I18, and fluid under pressure supplied to the chamber 60 will notflow therefrom by way of the passage I84 to the brake pipe.

The valve I82 prevents the flow of fluid from the brake cylinder 2 andthe auxiliary reservoir to the brake pipe while the diaphragm I34a is inengagement with the seat rib I36. This prevents the release offluid'from the brake cylinder and the auxiliary reservoir on an increasein the pressure of the fluid in the brake pipe until the brake pipepressure has been increased to a relatively high value, which is abovethat required to effect movement of the piston ID to the inner releaseposition.

This is desirable, because if cars equipped with I this type of brakecontrolling valve device are coupled into a train which includes carsequipped with older types of brake controlling valve devices, which donot vent fluid from the brake pipe to reduce the brake pipe pressuresubstantially to atmosphere on an emergency application of the brakes,some fluid under pressure may be supplied from the brake pipe on thosecars to the chamber I2 of this brake controlling valve device after thevent valve 96 has been moved to the seated position. This fluid maybuild up to a pressure great enough to cause the piston H) to be movedto the inner release position, and if fluid under pressure werepermitted to flow from the brake cylinder and auxiliary reservoir to thebrake pipe, the brake pipe pressure would be further increased, andmight result in movement of the service portion of the brake controllingvalve device to the release position to release the brakes.

The diaphragm I34a is not moved away from the seat rib I36, and thevalve I82 will not be unseated, until the pressure of the fluid in thebrake pipe is increased to a value somewhat higher than is required tocause movement of the piston ID to the inner release position. Thispressure is higher than that which will be present in the brake pipe andin the chamber I2 as a result of the flow of fluid thereto from the carsequipped with older types of brake controlling valve devices. As aresult, therefore, undesired flow of fluid from the brake cylinder andauxiliary reservoir to the brake pipe is prevented, even though thepiston I0 is moved to the inner release position.

On a further increase in the pressure of the fluid in the chamber I2,and in the chamber I44 on the face of the diaphragm I34a, the forceexerted by this fluid under pressure on the diaphragm IBM is sufficientto overcome the op posing force of the spring I38a, and the diaphragm.I34a is thereupon moved upwardly, as viewed in Fig. 2 of the drawings,away from the seat rib I36. As soon as the diaphragm I34a is moved awayfrom the seat rib I36, fluid under pressure flows from the chamber I44past the seat rib I36 to the chamber E52 outwardly of the seat rib, andbecause of the increased area of the diaphragm I34a subject to fluidunder pressure, there is a substantial increase in the force exerted onthis diaphragm, and it will be moved upwardly very rapidly until itsfurther movement is prevented by engagement of a portion of the plungerI62 with a portion of the housing of the emergency portion 8a.

On upward movement of the diaphragm 53411, the inwardly extending flangeI86 on the plunger II6 engages the flange I80 on the valve I82 and liftsthe valve away from its seat, thereby permitting fluid under pressuresupplied from. the brake cylinder 2 and the auxiliary reservoir, notshown, to the accelerated release check valve chamber 66, to flowtherefrom by way of the passage I84 to the chamber I44, from which itmay flow by way of the passage I48 and the choke I50 to the chamber I2on the face of the piston Ill, and thence by way of the passage I3 tothe brake pipe I to further increase the pressure of the fluid in thebrake pipe.

The fluid under pressure thus supplied to the brake pipe causes a localincrease in brake pipe pressure at each car which is transmittedserially throughout the train so as to secure movement of the pistons Iof the emergency portions of the brake controlling valve devices totheir inner release positions, and to also increase the pressure of thefluid in the brake pipe so as to effect movement of the diaphragms I340:away from the seat ribs I36.

In addition, on this upward movement of the diaphragm I34a the plungerI62 is moved up wardly and its movement is transmitted through thespring I66 to the valve II0 to move this valve to the seated position.On engagement of the valve I10 with its seat, and on further movement ofthe plunger I62, the spring I66 is compressed, the plunger I62 beingmoved relative to the valve I10. When the valve I10 is moved to theseated position communication between the valve chamber I6 and theatmosphere through the choke I64 is cut ofi.

Fluid under pressure willflow from the auxiliary reservoir, not shown,and the brake cylinder 2 to the brake pipe until the pressure of thefluid in the brake cylinder and the auxiliary reservoir and in the brakepipe has substantially equalized by the flow of fluid under pressurefrom the brake cylinder and auxiliary reservoir to the brake pipe. Theaccelerated release check valve 64 will then be moved into engagementwith the seat rib 68 by the spring 66 so as to cut off further flow offluid under pressure from the brake cylinder to the brake pipe, and toprevent back flow of fluid under pressure from the brake pipe to thebrake cylinder.

On movement of the diaphragm I34a away from the seat rib I36, and on thesupply of fluid under pressure from the brake pipe to the chamber I52outwardly of the seat rib I36, fluid under pressure will flow therefromby way of the passage I54 to the passage I56, and through the choke I58to the passage I08 leading to the valve chamber I6 and the pressurechamber I1, and to the chamber I06 of the valve device I02.

In addition, fluid under pressure supplied to the passage I54 flows tothe chamber II2 within the seat rib IIO, but, as pointed out above, thevalve I04 has previously been moved to the seated position by fluidunder pressure supplied from the chamber I44 through the passage I46 tothe chamber H8 at the face of the diaphragm The choke I58 restricts therate of flow of fluid from the brake pipe to the valve chamber I6 andthe pressure chamber IT, with the result that there is a slow rate ofincrease in the pressure of the fluid in these chambers.

After a time interval the pressure of the fluid in the chamber l6 willhave increased to a value such that the force exerted by the fluid inthis chamber, together with the force exerted by the spring 36 on thepiston I0, is able to overcome the opposing force of the fluid underpressure in the chamber I2, and the piston I0 will thereupon be moved tothe right, as viewed in Fig. 2 of the drawings, while the slide valve I8will be moved upon its seat to a position in which the cavity I62 nolonger establishes communication between the passage I64 and the passageI2.

When the piston I0 has moved from the inner release position to thenormal release position, the plunger 30 engages a portion of the body ofthe emergency portion 8a so that the spring 36 is no longer effective toeffect movement of the piston I0, and the higher pressure of the fluidin the chamber I2 prevents further movement of the piston I0 by thefluid under pressure in the chamber I6.

The rate of flow of fluid under pressure to the chamber I58 is such thatthe pressure of the fluid in the chamber I6 will not build up to a valuesuflicient to effect movement of the piston from the inner releaseposition to the normal release position until the piston I0 has been inthe inner release position for a period of time long enough to permitthe pressure of the fluid in the brake cylinder 2 and in the auxiliaryreservoir, not shown, to substantially equalize with the pressure in thebrake pipe.

After movement of the piston III to the normal release position, fluidunder pressure continues to flow from the brake pipe through the chokeI58 to the chambers I6 and I1, and to the chamber I06 of the valvedevice I02.

When the pressure of the fluid in the chamber I06 has increased to avalue such that the difference between the pressure of the fluid in thechamber I06, and in the brake pipe, and, therefore, in the chamber II8on the opposite face of the diaphragm H6, is less than a predeterminedamount, the spring I 26 will expand and will move the diaphragm H6 andthe plunger I20 downwardly until the spring seat I22 engages theinwardly extending flange I28 on the plunger I20. On a further reductionin the differential between the pressure of the fluid in the chamber I06and in the brake pipe, the spring II4 will move the valve I04 downwardlyaway from the seat rib I I0, and this movement of the valve I04 will betransmitted through the spring I26 to move the diaphragm II6 intoengagement with the projections I29.

After movement of the valve I04 away from the seat rib I I0, fluid underpressure supplied to the passage I54 flows to the chamber H2 and thencepast the seat rib H0 to the chamber I06, and therefrom by way of thepassage I08 to the chambers I6 and H to increase the pressure of thefluid in these chambers at a relatively rapid rate until the pressure ofthe fluid in these chambers has equalized with the pressure of the fluidin the chamber I2, and in the brake pipe I.

On an increase in the pressure of the fluid in the brake pipe I, fluidunder pressure flows therefrom by way of the branch pipe I4 and throughthe passages in the pipe bracket section I to the service portion, notshown, of the brake controlling valve device a, and when the pressure ofthe fluid supplied from the brake pipe I to the service portion hasincreased to a value exceeding the pressure of the fluid in theauxiliary reservoir, not shown, the service portion operates, asdescribed in detail in the above identified patent, to release fluidunder pressure from the brake cylinder 2, and to open a communicationthrough which fluid under pressure is supplied from the brake pipe I tothe auxiliary reservoir, and to the emergency reservoir 4.

It will be seen that the emergency valve portion shown in Fig. 2 of thedrawings, like that shown in Fig. 1 of the drawings, incorporates meansto cut off the flow of fluid from the brake pipe to the valve chamberuntil a pressure has been developed in the brake pipe which issufflcient to insure movement of the piston of the valve portion to aposition to completely open the communication through which fluid underpressure flows between the valve chamber and the brake pipe.

In addition, it will be seen that the emergency portion shown in Fig. 2of the drawings operates to cut oif the flow of fluid from the brakepipe to the valve chamber I6 until the pressure of the fluid in thebrake pipe has increased to a value great enough to cause movement ofthe piston of this valve portion to its inner release position, and alsothat the valve chamber is connected to the atmosphere until the passagethrough which fluid is supplied to this chamber is opened. This providesmeans to vent any fluid which leaks to the valve chamber while thepressure in the brake pipe is being increased, and insures thatsuflicient differential will be developed between the pressures in thebrake pipe and the valve chamber to cause movement of the piston to theinner release position.

'It will be seen also that means is provided to prevent the flow offluid from the brake cylinder and the auxiliary reservoir to the brakepipe, even though the piston moves to the inner release position, unlessthe brake pipe pressure is increased to a relatively high value, whichwill not be present following an emergency application of the brakes,except on an increase in brake pipe pressure to effect the release ofthe brakes.

While two embodiments of the improved brake controlling valve deviceprovided by my invention have been illustrated and described in detail,it should be understood that the invention is not limited to thesedetails of construction, and that numerous changes and modifications maybe made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is: v

1. In a fluid pressure brake equipment, in combination, a brake pipe,and an emergency valve device comprising a movable abutment subject tothe opposing pressures of the fluid in the brake pipe and of the fluidin a pressure chamber, a

passage controlled by said abutment through which fluid under pressuremay flow between the brake pipe and the pressure chamber in eitherdirection, and valve means controlling communication through saidpassage, said valve means being normally operative to cut offcormnunication through said passage and being operated to permitcommunication through said passage on an increase to a given value inthe pressure of the fluid supplied from the brake pipe to said passage.

2. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device'comprising a movable abutmentsubject to the opposing pressures of the fluid in the brake pipe and ofthe fluid in a pressure chamber, a passage through which fluid underpressure may flow between the brake pipe and the pressure chamber ineither direction, and valve means responsive to the pressure oi thefluid supplied from the brake pipe to said passage and controllingcommunication through said passage, said valve means being operated topermit communication through said passage on an increase to a givenvalue in the pressure of the fluid supplied to said passage.

3. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentconstantly subject to the opposing pressures of the fluid in the brakepipe and of the fluid in a pressure chamber, a passage through whichfluid under pressure may be supplied from the brake pipe to the pressurechamber, and valve means responsive to the pressure of the fluidsupplied to said passage and controlling communication through saidpassage, said valve means being operated to permit communication throughsaid passage on an increase to a given value in the pressure of thefluid supplied to said passage and to thereafter maintain communicationthrough said passage until the pressure of the fluid in said passage isreduced to a value substantially below said given value.

4. In a fluid pressure brake equipment, in combination, a brake pipe,and an emergency valve device comprising a movable abutment constantlysubject to the opposing pressures of the fluid in the brake pipe and ofthe fluid in a pressure chamber, a passage controlled by said abutmentthrough which fluid under pressure may be supplied from the brake pipeto the pressure chamher, and valve means responsive to the pressure ofthe fluid supplied to said passage and controlling communication throughthe passage, said valve means being adapted to cut oil the flow of fluidthrough said passage until the pressure of the fluid supplied to saidpassage has increased to a predetermined value and to maintaincommunication through said passage until the pressure of the fluid insaid passage is reduced to a value substantially below saidpredetermined value.

5. In a fluid pressure brake equipment, in combination, a brake pipe, avent valve for venting fluid under pressure from the brake pipe, amovable abutment subject to the opposing pressures of the fluid in thebrake pipe and of the fluid in a pressure chamber for controlling saidvent valve, a passage controlled by said abutment through which fluidunder pressure may flow between the brake pipe and the pressure chamberin either direction, and valve means subject to and operated on anincrease in the pressure of the fluid in said passage to opencommunication through said passage.

6. In a fluid pressure brake equipment, in combination, a brake pipe, avent valve for venting fluid under pressure from the brake pipe, amovable abutment subject to the opposing pressures of the fluid in thebrake pipe and of the fluid in a pressure chamber for controlling saidvent valve, a passage controlled by said abutment through which fluidunder pressure may flow between the brake pipe and the pressure chamber,and valve means subject to and operated on an increase to a given valuein the pressure of the fluid supplied to said passage to opencommunication through said passage, said valve means being adapted tomaintain communication through said passage until the pressure of thefluid in said passage is reduced to a value substantially below saidgiven value.

"7. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentconstantly subject to the opposing pressures of the fluid in the brakepipe and of the fluid in a pressure chamber, and valve means controllingthe supply of fluid under pressure from the brake pipe to the pressurechamber, said valve means comprising a movable abutment adapted to havesealing engagement with a seat surrounding an area on the face of theabutment and covering a portion only of the abutment, yieldingresistance means urging said abutment into engagement with the saidseat, the area on one side of said seat being in communication with thepressure chamber, and means for supplying fluid under pressure from thebrake pipe to the area on the other side of said seat.

8. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentsubject to the opposing pressures of the fluid in the brake pipe and ofthe fluid in a pressure chamber, and valve means controlling the supplyof fluid under pressure from the brake pipe to the pressure chamber,said valve means comprising a movable abutment adapted to have sealingengagement with a seat surrounding an area on the face of the abutmentand covering a portion only of the abutment, yielding resistance meansurging said abutment into engagement with the said seat, the area on oneside of said seat being in communication with the pressure chamber, andmeans controlled by said first abutment for supplying fluid underpressure from the brake pipe to the area on the other side of said seat.

9. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentsubject to the opposing pressures of the fluid in the brake pipe and ofthe fluid in a pressure chamber, said emergency valve device having apassage through which fluid may flow from the pressure chamber to thebrake pipe to reduce the pressure of the fluid in the pressure chambersubstantially as rapidly as the pressure of the fluid in the brake pipeis reduced in effecting a service application of the brakes, a valvedevice for controlling the flow of fluid through said passage from thebrake pipe to the pressure chamber, a by-pass passage extending aroundsaid valve device through which fluid may flow from the brake pipe tothe pressure chamber, and valve means responsive to the pressure of thefluid supplied to said passage for also controlling communicationthrough said passage.

10. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentsubject to the opposing pressures of the fluid in the brake pipe and ofthe fluid in a pressure chamber, said emergency valve device having apassage controlled by said abutment through which fluid may flow fromthe pressure chamber to the brake pipe to reduce the pressure of thefluid in the pressure chamber substantially as rapidly as the pressureof the fluid in the brake pipe is reduced in effecting a serviceapplication of the brakes, a valve device for controlling the flow offluid through said passage from the brake pipe to the pressure chamber,a by-pass passage extending around the valve device through which fluidmay flow from the brake pipe to the pressure chamber, and valve meansresponsive to the pressure of the fluid supplied to said passage foralso controlling communication through said passage.

11. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentsubject to the opposing pressures of the fluid in the brake pipe and ofthe fluid in a pressure chamber, a passage controlled by the abutmentthrough which fluid may flow from the pressure chamber to the brake pipeto reduce the pressure of the fluid in the pressure chambersubstantially as rapidly as the pressure of the fluid in the brake pipeis reduced in effecting a service application of the brakes, a valvedevice for regulating the flow of fluid through said passage from thebrake pipe to the pressure chamber, a supply passage controlled by saidabutment and through which fluid under pressure may flow from the brakepipe to the pressure chamber, and valve means responsive to the pressureof'the fluid supplied to said supply passage for controllingcommunication through said supply passage.

12. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, and an emergency valve device comprising a movable abutmentsubject to the opposing pressuresv of the fluid in the brake pipe and ofthe fluid in a pressure chamber, a passage controlled by the abutmentthrough which fluid may flow from the pressure chamber to the brake pipeto reduce the pressure of the fluid in the pressure chambersubstantially as rapidly as the pressure of the fluid in the brake pipeis reduced in effecting a service application of the brakes, a valvedevice for regulating. the flow of fluid through said passage from thebrake pipe to the pressure chamber, a supply passage controlled by saidabutment and through which fluid under pressure may flow from the brakepipe to the pressure chamber, and valve means responsive to the pressureof the fluid supplied to said supply passage for controllingcommunication through said supply passage, said valve means beingoperated to establish communication through said passage on an increaseto a given value in the pressure of the fluid supplied to said passageand to thereafter passage until the pressure of the fluid supplied tosaid passage is reduced substantially below said given value.

13. In a fluid pressure brake equipment for a vehicle, in combination, abrake pipe, a brake cylinder, valve means controlling a passage throughwhich fluid under pressure may be supplied from the brake cylinder tothe brake pipe, a movable abutment subject to the opposing pressures ofthe fluid in the brake pipe and of the fluid in a pressure chamber foroperating said valve means, yielding resistance means opposing movementof the valve means to a position to establish communication through saidpassage, a passage controlled by said abutment through which fluid underpressure may be supplied from the brake pipe to the pressure chamber,and a valve device responsive to the pressure of fluid supplied to saidpassage for controlling communication through said passage, said valvemeans being operated to cut off communication through said passage untilthe pressure of the fluid supplied thereto has increased to a givenvalue.

14. In a fluid pressure brake, in combination, a brake cylinder, a brakepipe, valve means controlling a passage through which fluid underpressure may be supplied from the brake cylinder to the brake pipe,movable abutment means subject to the opposing pressures of the fluid inthe brake pipe and of the fluid in a pressure chamber, the abutmentbeing operated to condition the valve means to permit communicationthrough said passage on an increase in the pressure of the fluid in thebrake pipe to a given value above the pressure of the fluid in thepressure chamber, a passage controlled by said movable abutment meansand through which fluid under pressure may be supplied from the brakepipe to the pres sure chamber, and a valve device responsive to thepressure of the fluid supplied to said passage for controllingcommunication through said passage, said valve device being operative tocut off communication through said passage until the maintaincommunication through said no

